This invention relates to the technical field of power electronics. It relates to a module housing according to the preamble of patent claim 1 and to a Power Semiconductor Module.
The development of IGBT (Insulated-Gate Bipolar Transistor) modules evolved from established Darlington transistor modules, which were the workhorse of the low voltage drives industry during the last two decades of the last century. Initially manufacturers simply replaced the Darlington chips with IGBT chips. This led to a diversity of packaging types in so-called xe2x80x9cstandard modulesxe2x80x9d. The lowest power devices tended to be in the 6-pack or full 3-phase bridge configuration. Higher current rated devices used the 2-pack or half-bridge configuration, while the highest current ratings were made in 1-packs (an IGBT with anti-parallel fast diode). This combination of evolution from bipolar modules with a diversified range of packages left a fragmented supply base, with a bewildering range of almost interchangeable modules. Suppliers were reluctant to move to standard solutions and invest in new tooling of packaging. Furthermore the old bipolar-derived packaging had a number of limitations when used with faster switching MOS gated IGBTs.
New generations of modules emerged, and there has been a great diversification in packaging, particularly in the low power range, with the suppliers introducing new concepts with higher levels of integration, usually aimed at particular parts of the market. By introducing more functionality into the devices suppliers are not necessarily able to produce a standard module in two senses of the word xe2x80x9cstandardxe2x80x9d. Firstly the additional functionality limits the area of application of the module. Secondly the standardization required by most users, namely multiple-sourcing, is more difficult to achieve between suppliers with different technology platforms.
In the lowest power range of the market the Econopacks as described in M. Feldvoxcex2 et al, xe2x80x9cA new compact inverter concept with low profile solderable ECONOPACK modulesxe2x80x9d, Powersystems World ""96 Conference, PCIM, Sep. 7-13, 1996, Las Vegas, were introduced and eventually reached the definition of a standard module: manufactured by more than one supplier and used by many customers. However until the introduction of LoPak, as described in S. Dewar et al, xe2x80x9cThe Standard Module of the 21st Centuryxe2x80x9d, ABB Semiconductors AG online documentation (www.absem.com), there was no new standard module, designed specifically for use with IGBT technology, above the 100A 6-pack rating. Conventional low power high voltage applications (line voltages above 3 kV) are controlled by GTOs (Gate Turn-Off Thyristors), IGCTs (Integrated Gate-Controlled Thyristor) or IGBTs. The IGBT, a device with several advantages compared to the thyristor-structured power semiconductors, e.g. low requirements regarding the driving unit, easy cooling resulting from the insulated structure, is fully developed and introduced for blocking voltages up to 6.5 kV. IGBT-Modules with blocking voltages of 4.5 or 6.5 kV have first been designed for traction inverters and have then been used for industrial drives as well as for power quality applications. The packaging kept the same standards as for lower voltage modules (1.2, 2.5 or 3.3 kV). All these modules have standard footprints, overall dimensions and terminal positions. Hence, all the creepage and clearance distances are identical and they all have the same electrical insulation. A 6.5 kV IGBT-Module is described in F. Auerbach, et al, xe2x80x9c6.5 kV IGBT-Modulesxe2x80x9d, EUPEC online documentation (www.eupec.com).,
For applications requiring even higher voltages series-connection of several modules is necessary. One possible way to reduce costs for these kinds of applications is to series-connect IGBT semiconductor chips inside a module, leading to modules with twice or three or even more times the blocking voltage of the highest voltage modules available today. However, for these high voltage modules conventional packaging design rules as applied in the LoPak modules have proven not be sufficient to ensure full insulation without any dielectric stress in critical areas of the module housings, e.g. glued junctions between two housing elements such as housing walls and covers.
It is therefore an object of the present invention to provide a module housing and a power semiconductor module of the initially mentioned kind with improved dielectric strength and increased blocking voltage capability.
This object is achieved with a module housing according to claim 1 and a power semiconductor module according to claim 4.
The inventive module housing comprises two electrically insulating housing elements that are attached to each other. A first of said housing elements comprises at least two openings for electric power terminals and a slot-like recess. Between the openings at least two insulating walls are arranged on and perpendicular to a surface of the housing. An at least one first of said insulating walls is part of a second of said housing elements and is inserted into the recess in said first housing element, while an at least one second of said insulating walls is part of the first housing element.
The insulating walls between the openings for the power terminals allow a compact arrangement of the terminals.
In a preferred embodiment of the inventive module housing, said second housing element with said first insulating wall being inserted into said recess and said first housing element are joined by a glued junction. This glued junction is separated from at least one of said openings by at least one of said second insulating walls.
The glue is not on the electrical clearance or creepage path between the power terminals in the openings. Any electrical field can therefore be applied to the glued junction, the path is always interrupted by at least one insulating wall between the junction and at least one of the terminals.
Further embodiments emerge from the depending claims.